The invention relates to a sealing ring, especially a radial shaft seal, piston seal, or rod seal, comprising a sealing disk having at least one fasting part provided on a first, preferably stationary, machine part, and wherein the sealing disk further has a seal part that is correlated with a second, preferably movable, machine part, preferably a shaft. The seal part extends in a direction toward an atmosphere side or medium side of the seal.
Radial shaft seals are known that have a dynamic seal part that is formed by an annular disk of polytetrafluoroethylene. In the mounted state of the sealing ring (seal), it is outwardly curved in the direction toward the air (atmosphere) side and rests with a sealing lip on the rotating machine part, usually a shaft. The size of this known sealing ring is relatively small. Moreover, because the sealing lip is oriented toward the air side of the sealing ring, a special protective lip or dust lip is not needed. This known sealing ring however entails the risk that already at minimal overpressure at the oil (medium) side the sealing lip will lift off the shaft so that the seal is no longer tight. This means, for example, that conventional seal-tightness tests for motors, carried out at only 0.3 bar overpressure, cannot be performed without additional measures by which the sealing location is covered during the test because, if this is not done, the sealing lip will lift off and thus cause leakage.
If such a sealing ring were to be modified in order to be used under pressure loads, the radial pressing force that tightly presses the sealing lip against the shaft would have to be increased to such an extent that the operating or testing pressure would not lift off the sealing lip. However, this would mean that during the generally pressure-free operation the increased radial force would increase the friction between the sealing lip and the shaft and therefore would increase also wear of the sealing lip and of the shaft. Moreover, increased wear would also lead to an increase of the temperature in the sealing gap between the shaft and the sealing lip which thus would increase the risk of so-called carbon fouling and thus of an untimely failure of the sealing ring. Such a sealing ring however has the advantage that when the seal is slipped onto the shaft or the shaft is introduced into the seal, the sealing disk will bend up because in the mounted position it is curved (or bulges) in the mounting direction. Moreover, it is possible that the sealing lip pushed onto the shaft can be checked with regard to possible mounting errors because it is not oriented inwardly but outwardly.
In a similar sealing ring, the sealing lip is curved in the opposite direction, i.e., counter to the mounting direction of the shaft. In order to prevent the sealing disk from turning upside down and thus the sealing disk from being damaged, this sealing ring must be inserted into a mounting sleeve for mounting it on the shaft.